Yeaah, the other stick will just down clock. ( Didnt you say you had 2000+ posts at the other forum, its hard to believe you never came across this with 2000+ posts lol)
Yes it will be way faster. It should work fine, the other ram should just downclock. What type of ram are you buying pc3200 correct? And you have pc3200 right now correct?
Well pc3200 is dual chanel ram. Each stick works at 200mhz each. The stick your buying will only run at 200mhz. Just buy that stick and you should be good too go.